The present invention relates to a control apparatus for an automatic transmission. The control apparatus controls the shift-state of the automatic transmission on the basis of a selected shift-mode. When selection is switched from an automatic shift-mode to a manual shift-mode, the automatic shift-control apparatus changes the shift-stage or a shift-range to a speed that is lower than the current shift-stage. Further, the present invention relates to a method for controlling the automatic transmission.
FIG. 8 of Japanese Patent No. 3017501 discloses a downshifting process. If the driver operates a shift-lever to change the shift-mode of an automatic transmission from an automatic shift-mode “D” to a manual shift-mode “M”, the shift-stage of the automatic transmission is changed to low speed by one or two stages in the downshifting process. The downshifting process provides the driver with sporty drive feel.
If a power-supply voltage is reduced or load to be processed is excessively increased, the control apparatus for an automatic transmission some times initializes itself like when the power-supply has just been activated.
If the control apparatus initializes itself, data about shift-modes stored in a memory is lost in some cases. Suppose that, for example, the initialization occurs a shift-mode obtained before the initialization has been a manual shift-mode “M”. When the data of the memory is lost due to the initialization, the data of the memory may temporarily be an automatic shift-mode “D”. The control apparatus changes the data of the memory to the manual shift-mode “M” by detecting the state of the shift-lever after the initialization. Considering the data of the memory from a point of view of the control apparatus, the initialization of the control apparatus means that the driver has operated the shift-lever to change the shift-mode from the automatic shift-mode “D” to the manual shift-mode “M”. Accordingly, when the initialization occurs, the control apparatus performs a downshifting process. In other words, there is a concern that an unintended downshifting process may be performed during the drive regardless of the driver's operation of the shift-lever.
The problem of the vehicle drivability can be caused by temporary loss of an output signal of a shift-lever sensor as well as the initialization of the control apparatus.
An objective of the present invention is to prevent the vehicle drivability from deteriorating.
According to one aspect of the present invention, there is provided a control apparatus for controlling a shift-stage of an automatic transmission. An upper limit of a control range of the shift-stage may be set by setting a shift-range. The automatic transmission is operated to select one of a plurality of shift-modes including an automatic shift-mode and a manual shift-mode. The automatic transmission includes a mode-operation detecting section. The mode-operation detecting section detects the selecting operation to obtain a mode-detection value. A power-supply voltage is supplied to the control apparatus. The control apparatus includes a shift-stage control section that controls the shift-stage on the basis of the mode-detection value. The shift-stage control section changes the shift-stage or the shift-range to speed lower than speed that is obtained before the switching of the mode-detection value if the mode-detection value is switched from the automatic shift-mode to the manual shift-mode. The shift-stage control section may be in a recognizable-state, in which the shift-stage control section is capable of recognizing the mode-selection value, or an unrecognizable-state, in which the shift-stage control section is not capable of recognizing the mode-selection value. A holding section holds a value of the shift-stage or the shift-range as a hold value. The holding section continues to hold the hold value regardless of the reduction of the power-supply voltage. A return determining section determines that the shift-stage control section returns to the recognizable-state from the unrecognizable-state. A return-time adjusting section sets the shift-stage to the hold value after the return of the shift-stage control section. The return-time adjusting section controls the shift-stage in the automatic shift-mode over a standby-period after the return. The return-time adjusting section controls the shift-stage in the automatic shift-mode until the selecting operation is detected after the standby-period passes.
Further, according to another aspect of the present invention, there is provided a control apparatus for an automatic transmission. A return-time adjusting section observes whether a mode-detection value is in the manual shift-mode over the standby-period after the return of a shift-stage control section. The return-time adjusting section sets a shift-stage or a shift-range to the hold value if determining that the mode-detection value is in the manual shift-mode. Until the standby-period passes, the return-time adjusting section then controls the shift-stage in the manual shift-mode until the detection of the selecting operation.
According to another aspect of the present invention, there is provided a control method of controlling a shift-stage of an automatic transmission. An upper limit of a control range of the shift-stage may be set by setting a shift-range. The automatic transmission is operated as to select one of a plurality of shift-modes including an automatic shift-mode and a manual shift-mode. The automatic transmission includes a mode-operation detecting section. The mode-operation detecting section detects the selecting operation to obtain a mode-detection value. A power-supply voltage is supplied to the automatic transmission. The control method includes controlling the shift-stage on the basis of the mode-detection value, and changing the shift-stage or the shift-range to a speed lower than a speed that is obtained before the switching of the mode-detection value, when the mode-detection value is switched from the automatic shift-mode to the manual shift-mode. Further, the control method includes holding a value of the shift-stage or the shift-range as a hold value and continuing to hold the hold value regardless of the reduction of the power-supply voltage, and determining that a state returns to a recognizable-state, in which a mode-selection value can be recognized, from an unrecognizable-state, in which the mode-selection value cannot be recognized. Furthermore, the control method includes setting the shift-stage to the hold value after the return, and controlling the shift-stage in the automatic shift-mode over a standby-period after the return. In addition, the control method includes controlling the shift-stage in the automatic shift-mode until the selecting operation is detected after the standby-period passes.
According to another aspect of the present invention, there is provided a control method of controlling a shift-stage of an automatic transmission. The control method includes observing whether a mode-detection value is in a manual shift-mode after return over a standby-period. Further, the control method includes setting a shift-stage or a shift-range to a hold value if it is determined that the mode-detection value is in the manual shift-mode during the standby-period. Furthermore, the control method includes controlling the shift-stage in the manual shift-mode until the detection of the selecting operation until the standby-period passes.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.